The ENFR I/II mixed-mode fracture test analyzes the interlarminar fracture in fiber reinforced composites. These materials are widely used in wind turbine blades. At the structural scale, one of the most critical failures in a blade is delamination of unidirectional laminates in the spar cap. In this paper we introduce a new methodology for mixed fracture mode analysis based on linear elastic fracture mechanics (LEFM). In order to demonstrate the consistence of the theoretical basis of the methodology, ENFR test method is applied to 10 different test conditions in specimens of one composite material typically used in wind turbine blades. Experimental results obtained for critical fracture parameters, agree with the ones obtained in pure mode fracture tests. Therefore the method can be used for wind turbine blade material characterization, at coupon testing level, as the experimental results demonstrate.